Question

X-rays are used for the determination of crystal structure because:

• A. They can travel in a vacuum
• B. They are radioactive
• C. Their wavelength is of the same order as interplanar spacing in crystals
• D. Their speed changes with the change of medium

Hint:

X-rays used for structural analysis have wavelengths that are of the same order as atomic distances in the crystalline solids. This makes them suitable to study the interatomic distances. XRD patterns can also tell us about the different crystalline phases and the defects present in the crystalline lattice.

Answer 1

The Correct Option is C

X-rays are ideal for determining crystal structures because their wavelengths (approximately 0.1–10 nm) match the interplanar spacing of crystal lattices. This enables constructive interference when X-rays interact with atoms in the crystal, following Bragg’s law:
\(n\lambda = 2d \sin \theta\)
where:
$n$: Order of diffraction.
$\lambda$: Wavelength of X-rays.
$d$: Interplanar spacing.
$\theta$: Angle of incidence.
The diffraction pattern generated by this interaction is analyzed to determine the atomic arrangement and symmetry in the crystal.